Biography:

In the past J.G.S. Duque has collaborated on articles with L.A. Valenzuela and E.A. Souza. One of their most recent publications is Structural and magnetic properties of nanocrystalline particles in an amorphous Fe73.5Nb3CuSi13.5B9 matrix. Which was published in journal Journal of Non-Crystalline Solids.

More information about J.G.S. Duque research including statistics on their citations can be found on their Copernicus Academic profile page.

J.G.S. Duque's Articles: (14)

Structural and magnetic properties of nanocrystalline particles in an amorphous Fe73.5Nb3CuSi13.5B9 matrix

AbstractWe report structural and magnetic properties of fine particles embedded in an amorphous magnetic matrix. As-quenched amorphous Fe73.5Nb3CuSi13.5B9 ribbons (FINEMET) were submitted to the thermal treatments of several times (1 ⩽ t ⩽ 240 min) at 570 °C using a conventional furnace. The analyses of the X-ray diffraction patterns at room temperature reveal that our samples consist of single phase Fe3Si nanocrystals embedded in a residual amorphous phase. Magnetic measurements show that the saturation moment at T = 450 °C increases as a function of annealing time. This behavior is attributed to an increase of the fraction of nanocrystallites in the residual amorphous phase.

Synthesis and characterization of NiO and NiFe2O4 nanoparticles obtained by a sucrose-based route

AbstractCrystalline oxide powders were synthesized in nanoscale dimensions by a simple and novel chemical route, which is based on the use of sucrose as a chelating agent. The starting solutions were evaporated at 60∘C and the resulting gel was heated up to 300, 600 or 750∘C. The process was able to produce nickel oxide and nickel ferrite, characterized by structural and microscopic techniques. The average size of the particle was estimated by both Scherrer's equation and electron microscopy, and the results indicated that particles with a high crystallinity and a mean size in the range of 11–36 nm were obtained. This synthesis route was able to produce NiFe2O4 and NiO nanoparticles at temperatures as low as 300 and 350∘C, respectively.

Physical properties of antiferromagnetic single crystal GdIn3

Highlights•We have observed a transition phase AFM to PM.•The frustration parameter bigger than one.•The magnetic entropy is not recovered at TN.•In low temperatures is observed anomaly consistent with spins reorientation and/or ferromagnetic phase.

Electron spin resonance (ESR) in multiferroic TbMnO3

AbstractWe report temperature dependent X-Band (ν∼9.4GHz) electron spin resonance (ESR) measurement in a single crystal of TbMnO3. A single Lorentzian ESR line with an isotropic g∼ 1.96 was observed for T⩾120K up to 600 K. The ESR signal is attributed to the Mn3+ ions in a insulator environment. For the three crystallographic axes the temperature dependence ESR linewidth shows a strong broadening as the temperature decreases due to the presence of short range magnetic correlations.

Field induced phase transitions on NdRhIn5 and Nd2RhIn8 antiferromagnetic compounds

AbstractIn this work, we have investigated the low temperature magnetic phase diagram of the tetragonal NdRhIn5 and Nd2RhIn8 single crystals by means of temperature and field dependent heat capacity and magnetic susceptibility measurements. These compounds order antiferromagnetically with a Néel temperature (TN) of 11 and 10.7 K for NdRhIn5 and Nd2RhIn8, respectively. The constructed magnetic phase of both compounds are anisotropic and show, as expected, a decrease of TN as a function of the magnetic field for c crystallographic direction. However when the magnetic field is applied along of the c-axis, which is the magnetic easy axis, first-order-like field induced transitions are observed within the antiferromagnetic state. We compare the phase diagrams obtained for NdRhIn5 and Nd2RhIn8 with those for their cubic relative NdIn3.

Research articlesTailoring the structural and magnetic properties of Co-Zn nanosized ferrites for hyperthermia applications

Highlights•Structural, magnetic and hyperthermia studies of CoxZn1−xFe2O4 nanoparticles.•Maximum magnetization values for x = 0.5 associated to cation distribution.•Decrease in Curie point and magnetocrystalline anisotropy with Zn content.•Occurrence of canted spin arrangement (Y-K angle).•Optimum self-controlled temperature hyperthermia agents.

Non-linear magetoinductance in amorphous wires

AbstractThe second harmonic of the magnetoinductance (MI) signal of a melt-extracted amorphous magnetic wire varies significantly with the strength of the DC axial field applied to the wire. Its amplitude at frequencies between 200 kHz and 1 MHz was measured with a spectrum analyzer. We found that it has a four-peak structure, and that the peak amplitude increases with the frequency of the driving current. When a tensile stress is applied to the wire, the central peaks diminish, while the outer peaks are more widely spaced on the field axis. A simple analytical model of the MI signal shows that a large second harmonic of this signal and a large asymmetry in the circumferential hysteresis loop of the wire occur together and are manifestations of the same material property.

Exchange interaction effects in the ESR spectra of Eu2+ in LaB6

AbstractThe electron spin resonance (ESR) spectra of Eu2+ (4f7,S=72) in LaB6 single crystal show a single Dysonian resonance for the localized Eu2+ magnetic moments. It is shown that the Eu2+ ions are covalent exchange coupled to the (B) 2p-like host conduction electrons.

Field-dependent collective ESR mode in YbRh2Si2

AbstractElectron spin resonance (ESR) experiments in YbRh2Si2 Kondo lattice (TK≃25K) at different field/frequencies (4.1≤ν≤34.4GHz) and H⊥c revealed: (i) a strong field dependent Yb3+ spin–lattice relaxation, (ii) a weak field and T-dependent effective g-value, (iii) a suppression of the ESR intensity beyond 15% of Lu-doping, and (iv) a strong sample and Lu-doping (≤15%) dependence of the ESR data. These results suggest that the ESR signal in YbRh2Si2 may be due to a coupled Yb3+-conduction electron resonant collective mode with a subtle field-dependent spins dynamic.

Influence of organic precursor on the structural and magnetic properties of Co3O4 nanoparticles

AbstractAntiferromagnetic Co3O4 nanoparticles were synthesized by the coprecipitation method. With the addition of the sucrose as chelating agent (sucrose) the size of the particles was reduced from 54 nm to 19 nm. The Co3O4 nanoparticles exhibit a cubic spinel structure identified for X-ray diffraction (XRD) and confirmed by Rietveld refinement. Scanning Electron Microscopy (SEM) images exhibit a spherical-like morphology and confirm the decrease of the particle size observed by XRD. The magnetic measurements as a function of temperature using a superconducting quantum interference device (SQUID) show a large surface anisotropy for samples obtained with the addition of sucrose accompanied by an exchange Bias effect indicating also the existence of a weak ferromagnetism. A decrease of the Néel temperature from the bulk (and other nanostructures-type) was observed, which can be associated with finite-size effect in the nanoparticles' shape.

Analysis of zero field and field cooled magnetization curves of CoFe2O4 nanoparticles with a T-dependence on the saturation magnetization

Highlights•The T- dependence on saturation magnetization were considered in analysis of ZFC-FC curves.•CoFe2O4 nanoparticles embedded inside an amorphous SiO2 were produced by the sol-gel method.

Study of the dynamic of crystallization of an amorphous Fe40Ni40P14B6 ribbon through Johnson-Mehl-Avrami model

Highlights•The Johnson-Mehl-Avrami model was used to investigate the dynamic of crystallization.•Thermogravimetry technique was used to observe magnetic phase transition.•The crystallization processes occur by diffusion-controlled growth.•The crystallized fraction takes an important in the magnetic properties.

ReviewDoping the intermetallic compound ErNi3Al9 with Cu: A structural and magnetic characterization of a phase transition

Highlights•Effect Cu-doping on the structural and magnetic properties of the ErNi3Al9 compound.•Change in crystalline symmetry from trigonal R32 to tetragonal I4/mmm.•The transition temperatures across the series are unaffected by the doping.•The phase of transition is evident in the crystalline field effects.

Observation of magnetic-field-induced transitions in the DyNi3Ga9 intermetallic compound

Highlights•Intermetallic Compound.•Susceptibility.•Specific Heat.•Magnetic Phase Transition.

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